"On Liberty" by John Stuart Mill

One-paragraph review:
It would be a fairly large act of hubris to try to review "On Liberty" as if it weren't a well-established classic of political and philosophical thought. But it is worth noting that even a century and a half past its publication, John Stuart Mill's work is nearly as fresh and relevant as ever. Putting aside the characteristic mid-19th-Century run-on sentences (a handicap that makes it hard to cite Mill in the social-media-driven arguments of today), "On Liberty" addresses questions of the relationship between the individual and his or her government that are persistent throughout modern history.
One could reasonably argue that these are persistent questions because they reflect certain hazards inherent to state power: A lust for power, overestimation of one's ability to decide for others, the urge to "protect" the community against things it does not like. Mill is stridently against these human shortcomings, because he is stridently for humane virtues.
But it is also worth noting that Mill is the proto-libertarian whom today's anarcho-libertarians forgot. While again and again Mill rails against the abuse of power (and he sets the bar for what constitutes abuse quite low), he isn't against government per se. He is realistic about the tradeoff between perfect liberty and the inevitable limits upon it.
Yet his philosophy has an urgent message for the masses today who think of government as a source of things (from rights to remuneration), rather than a guarantee of their natural rights to exist peaceably with one another. Today, as always before and probably always in the future, Mill's words are essential.